Purified carboxylic acids, particularly aromatic dicarboxylic, acids are industrially important chemicals. For example, polymer grade benzene-1,4-dicarboxylic acid (also referred to as terephthalic acid or TPA) of chemical formula C6H4(COOH)2 can be a starting material for the formation of polyester resin, which can be used to make many materials of commerce having a variety of utilities.
The production of TPA can include liquid phase oxidation of an aromatic hydrocarbon. This process, however, can result in a product which includes impurities such as 4-carboxybenzaldehyde (4-CBA). The amount of 4-CBA produced by this process can be 1,000 parts per million to 10,000 parts per million. These impurities are undesirable as they can include chain termination agents, colored impurities, and other reaction by-products. Because these impurities affect product quality (e.g., color, material properties, and the like) they reduce the value of the TPA product if not removed. As a result, the crude TPA often undergoes cumbersome purification processes.
Thus, there remains a desire in industrial production of TPA to reduce or eliminate the production of impurities and/or to simplify the TPA production process.